Air filters

ABSTRACT

This invention relates to self cleaning air filters of the type in which the operative filter elements are periodically cleaned during the operation of the filter by reversing the flow of air through these elements; and is particularly, though not exclusively concerned with such filters of comparatively large air flow capacity. The invention provides a self cleaning air filter unit comprising an inlet chamber and an outlet chamber, a filter wall arranged to separate the inlet chamber from the outlet chamber, a plurality of filter elements arranged on the filter wall in an array of cross-wise rows over a length of the filter wall to allow air to pass from the inlet chamber to the outlet chamber through the filter elements, a gantry arranged in the outlet chamber across said array for traverse along the length of the array, a plurality of reverse air flow nozzles arranged on the gantry to register successively with the filter elements on each row of the filter elements, and means for supplying air to the nozzles to exit therefrom at such speed that in use of the filter unit the flow of air from the inlet chamber to the outlet chamber is reversed through a filter element when it is in alignment with a nozzle.

United States Patent [191 Deuce Dec. 11, 1973 AIR FILTERS 22 Filed: June18, 1971 21 Appl. No.: 154,439

[30] Foreign Application Priority Data Mar. 30, 1971 Great Britain8,144/71 [52] U.S. Cl 55/287, 55/294, 55/302, 55/341, 55/377, 55/379[51] Int. Cl B0ld 46/04 [58] Field of Search 55/302, 272, 273,

55/282, 283,284, 286, 287, 288, 293, 294, 341, 374, 376, 377, 378, 379,381, DIG. 26; 210/323, 333, 451, 457

OTHER PUBLICATIONS French Printed Application No. 2009625, Printed 2--6-70, (3 sht. dwg., 9pp. spec.)

Primary Examiner-Dennis E. Talbert, Jr. Att0rneyKarl W. Flocks [57]ABSTRACT This invention relates to self cleaning air filters of the typein which the operative filter elements are periodically cleaned duringthe operation of the filter by reversing the flow of air through theseelements; and is particularly, though not exclusively concerned withsuch filters of comparatively large air flow capacity. The inventionprovides a self cleaning air filter unit comprising an inlet chamber andan outlet chamber, a filter wall arranged to separate the inlet chamberfrom the outlet chamber, a plurality of filter elements arranged on thefilter wall in an array of cross-wise rows over a length of the filterwall to allow air to pass from the inlet chamber to the outlet chamberthrough the filter elements, a gantry arranged in the outlet chamber.across said array for traverse along the length of the array, aplurality of reverse air flow nozzles arranged on the gantry to registersuccessively with the filter elements on each row of the filterelements, and means for supplying air to the nozzles to exit therefromat such speed that in use of the filter unit the flow of air from theinlet chamber to the outlet chamber is reversed through a filter elementwhen it is in alignment with a nozzle.

2 Claims, 6 Drawing Figures Pmmmmn ms 3,777,458

SHEET 10F 4 INVENTOR- GEUFFREY R. DENCE Br K [J H006 A TORNEY PATENTEDDEC 1 1 i973 SHEET 3 BF 4 AIR FILTERS BACKGROUND OF THE INVENTION Thisinvention relates to self cleaning air filters of the type in which theoperative filter elements are periodically cleaned during the operationof the filter by reversing the flow of air through these elements; andis particularly, though not exclusively, concerned with such filters ofcomparatively large air flow capacity.

In a number of industrial processes it is necessary to filter dust andlarger particulate matter from air which has circulated through aprocessing plant, either as a direct part of the process or by way ofventilation and airconditioning, before the air can be released again toatmosphere or recirculated. A particular, but not exclusive example of aprocess where the present invention finds application, is in theprocessing of asbestos ores. In the processes used it is necessary toremove dust and fine particles of asbestos material from largequantities of air which has been used in the process of separating theasbestos from its ore. It is desirable that the filters used are selfcleaning so that the plant operation need not be interrupted while thefilters are cleaned and the filtrate removed.

With previous designs of self cleaning filters, in order to handle thelarge quantities of air to be filtered, it has been necessary to use alarge number of individual filter units because with previous designs ofself cleaning filters there has been a limit to the number of and sizeof individual filter units which can be accommodated. This has beenwasteful in space within the plant and particularly in electrical powerconsumption as each individual filter unit has required a separate motorto drive a fan for producing the cleaning reverse air fiow through thefilter elements.

It is an object of the present invention to provide an arrangement forself cleaning filters which can accommodate a large number of filterelements within a single filter unit.

SUMMARY OF THE INVENTION Accordingly in one aspect the present inventionprovides a self cleaning air filter unit comprising an inlet chamber andan outlet chamber, a filter wall arranged to separate the inlet chamberfrom the outlet chamber, a plurality of filter elements arranged on thefilter wall in an array of cross-wise rows over a length of the filterwall to allow air to pass from the inlet chamber to the outlet chamberthrough the filter elements, a gantry arranged in the outlet chamberacross said array for traverse along the length of the array, aplurality of reverse air flow nozzles arranged on the gantry to registersuccessively with the filter elements of each row of the filterelements, and means for supplying air to the nozzles to exit therefromat such speed that in use of the filter unit the flow of air from theinlet chamber to the outlet chamber is reversed through a filter elementwhen it is in alignment with a nozzle.

In a preferred arrangement of the invention the means for supplying airto said nozzles comprises an electrically driven fan unit mounted onsaid gantry.

In a further preferred arrangement the means for supplying air to saidnozzles comprises an electrically driven fan unit mounted outside saidoutlet chamber and connected to said inlet port of said manifold bymovable ducting.

Preferably in any of the above arrangements of the invention, the filterelements comprise filter sleeves supported against flow through them bymeans of open lattice cylindrical supports within them. Preferably thefilter sleeves are so clamped in groups by means of plates bolted orotherwise removably attached to that surface of the filter wall.

BRIEF DESCRIPTION OF THE DRAWINGS In order to promote a fullerunderstanding of the above, and other, aspects of the present invention,two embodiments will now be described, by way of example only, withreference to the accompanying drawings in which:

FIG. 1 is a schematic cross-sectional perspective view of a firstembodiment.

FIG. 2 is a plan view of the embodiment of FIG. 1,

FIG. 3 is a part cross-sectional scrap view of the mounting of theindividual filter elements of FIG. 1,

FIG. 4 is a plan view of the reverse air apparatus of a secondembodiment,

FIG. 5 is an end view of the apparatus of FIG. 4, and

FIG. 6 is a side view of the nozzle assembly of the apparatus of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1 and2, there is shown a high capacity filter for filtering process air. Thefilter comprises a lower chamber 10 into which air to be filtered isconveyed by means of ducting (not shown) and which is separated, bymeans of a filter wall 11, from an upper chamber 12 out of whichfiltered air is conveyed by means of ducting (not shown). The filterwall 1 1 extends over the whole interface between the chambers l0 and 12and is formed with an array of crosswise rows of apertures 13 in each ofwhich is supported an air filter element 14. The filter elements 14include a sleeve 15 of filter material, the lower end 16 of the sleeve15 being closed, and the upper end 17 being sealed to the filter wall 11around the aperture 13. Thus any air passing from the chamber 10 to thechamber 12 must pass through one of the filter sleeves 15, thus beingfiltered.

A gantry generally indicated at 20 is provided in the chamber 12 abovethe filter wall 11 and arranged to extend across the width of the arrayof filter elements and traverse along rails 21 over the length of thearray of filter elements in the direction of the arrows 22 shown in FIG.2. A re-circulating chain mechanism (not shown) driven by an electricmotor is provided to traverse the gantry along the rails 21, the motorpreferably being mounted outside the chamber 12.

The gantry 20 includes an air manifold 23 which distributes air from aninlet port 24 substantially equally to a plurality of air nozzles 25provided along its lower surface. The nozzles 25 are spaced along theduct 23 in such manner that they align respectively with the filterelements 14 in a cross-wise row of the array. Movement of the gantryalong its rails over the length of the filter unit thus brings thenozzles 25 successively into alignment with each cross-wise row offilter elements.

An electrically driven fan unit 30 is mounted on the casing of thefilter unit outside the chamber 12 and arranged to blow air in throughthe wall of the chamber 12 by means of an inlet port 31, the inlet port31 is connected to the inlet port 34 of the manifold 23 by means ofjointed ducting indicated generally at 32. The jointed ducting 32comprises a first duct 33 which is connected to the inlet port 31, bymeans of a swivel joint 34, a second duct 35 connected to the first ductby means of a swivel joint 36 and connected to the inlet 24 by means ofa swivel joint 37. The arrangement as best seen in FIG. 2 is such thatthe ducts 33 and 35 allow a scope of movement of the gantry 20 to coverthe whole length of the array of filter elements.

In operation, air from a process to be filtered flows into the chamber10, through the filter elements into the chamber 12, and out toatmosphere or possibly recirculation through the process During theoperation of the filter, the fan 30 is in continuous operation supplyingair to the nozzles 25 which exits from those nozzles at a high velocity.The gantry 20 is traversed backwards and forwards over the length of thearray of filter elements so that the air from the nozzles 25 passes downinto respective ones of a cross-wise row of filter elements for a givenperiod of time during each such traverse.

The velocity of the air leaving the nozzles 25 is such that it issufficient to reverse the flow of air through the filter sleeves of thatrow which the nozzles are aligned with, thus causing the material whichhas collected on the outside of the respective filter sleeves 16 in thecourse of their filtering action, to be blown off the outside and tofall into the bottom of the chamber to gather there and subsequently beremoved through a suitable shutter, indicated generally at 37, onto aconveyor.

As best seen in FIG. 3, the filter sleeves are supported from the filterwall 11 and held in shape against the inward flow of air from thechamber 10 during operation of the filter by means of a cage 40, thecage 40 is constructed of wire of rod material to form an opencylindrical lattice to support the inside of the filter sleeve and issupported from the filter wall 11 by means of a shaped flange 41attached to its upper end. The filter sleeve 15 is rolled over a shapedresilient annular former 42 and suitably reinforced as indicated at 43to be supported by the former 42. The former 42 rests on and sealsagainst the upper surface of the filter wall 11 and is held down firmlyin such position by the flange 41 of the respective cage to retain it inthat position. A clamping plate 45 is removably attached to the filterwall 11 by means of bolts 44 and is arranged to engage and retain anumber of cage flanges 41 and their respective filters, typically apattern of six adjacent filter elements. Thus by removing a plate 45 thefilter elements retained by it can be readily replaced withoutdisturbing the remainder at any time.

The design of the chamber 10 and of the ducts by which air is fed to itis arranged so that during operation of the filter the air in thechamber 10 is comparatively still thus allowing the dust and otherparticles removed from the filter bags to settle in the bottom of thechamber. To further enhance the removal of dust and other particles fromthe filter sleeves, use is made of the fact that when the nozzles 25come into alignment with the filter sleeves, the air flow is suddenlyreversed with the result that the filter sleeves snap from the positionwhere they are urged outwards by the reversed air flow from the nozzles25 thus imparting a shaking action to the sleeves.

The above discussed embodiment is particularly suitsble for use infiltering hot gases because the fan unit for the reverse air supply ismounted outside the filter chambers, and thus not exposed totemperatures of the hot gas being filtered, leaving only the ducting andnozzle gantry inside the chamber which items may be more readilyconstructed to resist the temperature.

FIGS. 4, 5 and 6 show an alternative embodiment which may be used wherethis last point is not a particular problem. In this embodiment which isotherwise similar to the previously described one, the gantry is ofgenerally similar arrangement as indicated at 50, but carried a fan unitfor the provision of reverse air flow inside the chamber 12. The gantry50 is mounted in a similar manner for travel along a length of an arrayof filter elements and is similarly provided with a plurality of nozzles51 which receive air by way of a manifold 52 from the fan unit 53. Inorder that an electrical supply may be carried to the motor 54 whichdrives the fan unit, a self coiling cable reel 55 is mounted on thegantry adjacent the motor 54 so that it will coil or uncoil a supplycable extending to one end of the filter chamber 12 as the gantrytraverses.

A further feature illustrated particularly in FIGS. 5 and 6 which isapplicable to either arrangement of the gantry is the provision of aflexible curtain assembly around the bottom of the reverse air flownozzles. This flexible curtain indicated at 56 forms a shroud around allthe nozzles to extend to just above the upper surface of the variousclamping plates on the filter wall 11 thus to enhance the efficiency ofreverse air flow by restricing the escape of air around the nozzles intothe chamber 12.

Thus it can be seen that with the arrangement of the invention it ispossible to provide, and arrange for the cleaning of a large number offilter elements in a self cleaning filter unit. The array of elementsmay be made virtually any size to suit the flow handling requirements ofthe filter unit, and if a particularly large unit is needed two or moregantries of reverse flow nozzles of either type may be provided in asingle unit, each being arranged for the cleaning of a particular partof the array.

The embodiments of the invention to which an exclusive property orprivilege is claimed are defined as follows:

1. A self cleaning air filter unit comprising an inlet chamber and anoutlet chamber, a filter wall arranged in a horizontal plane to separatethe inlet chamber from the outlet chamber, a plurality of filterelements arranged on the filter wall in an array of cross-wise rows overa length of the filter wall to allow air to pass from the inlet chamberto the outlet chamber through the filter elements, each said filterelement comprising a filter sleeve sealed around one end to theperiphery of an aperture in said filter wall and closed at the otherend, and an open lattice cylindrical support cage arranged within thesleeve and mounted on said filter wall, said one end of each of saidfilter sleeves being provided with a resilient annular former, thematerial of the sleeve being rolled over the former and reinforced atthat point, and said support cages being each provided with a flange,said flange being arranged to grip said former between itself and a faceof said filter wall, a plurality of clamping plates each releasablyattached to said filter wall and arranged to engage and retain aplurality of said support cages, a gantry arranged in the outlet chamberacross said array for traverse along the length of the array, aplurality of reverse air flow nozzles arranged on the gantry to registersuccessively with the filter elements of each row of the filterelements, a manifold having an inlet port mounted on said gantry andarranged to distribute air from the inlet port to said nozzles, thenozzles being mounted along a face of the manifold opposed to saidfilter wall, a flexible curtain arranged on the gantry around theoutlets of all said nozzles to form a shroud therearound, the curtainextending substantially to said filter wall, and means for supplying airto the nozzles to exit therefrom at such speed that in use of the filterunit the flow of air from the inlet chamber to the outlet chamber isreversed through a filter element when it is in alignment with a nozzle,said air supply means comprising an electrically driven fan unit mountedoutside said outlet chamber and movable ducting connecting said inletport of the manifold to said fan unit.

2. A self cleaning air filter unit according to claim 1, wherein saidmovable ducting comprises a first duct, a port in a wall of said outletchamber, said first duct being connected to said port by means of afirst swivel joint, a second duct and a second swivel joint arrangedbetween the first and second ducts, and a third swivel joint arrangedbetween the second duct and said inlet port of said manifold.

1. A self cleaning air filter unit comprising an inlet chamber and anoutlet chamber, a filter wall arranged in a horizontal plane to separatethe inlet chamber from the outlet chamber, a plurality of filterelements arranged on the filter wall in an array of cross-wise rows overa length of the filter wall to allow air to pass from the inlet chamberto the outlet chamber through the filter elements, each said filterelement comprising a filter sleeve sealed around one end to theperiphery of an aperture in said filter wall and closed at the otherend, and an open lattice cylindrical support cage arranged within thesleeve and mounted on said filter wall, said one end of each of saidfilter sleeves being provided with a resilient annular former, thematerial of the sleeve being rolled over the former and reinforced atthat point, and said support cages being each provided with a flange,said flange being arranged to grip said former between itself and a faceof said filter wall, a plurality of clamping plates each releasablyattached to said filter wall and arranged to engage and retain aplurality of said support cages, a gantry arranged in the outlet chamberacross said array for traverse along the length of the array, aplurality of reverse air flow nozzles arranged on the gantry to registersuccessively with the filter elements of each row of the filterelements, a manifold having an inlet port mounted on said gantry andarranged to distribute air from the inlet port to said nozzles, thenozzles being mounted along a face of the manifold opposed to saidfilter wall, a flexible curtain arranged on the gantry around theoutlets of all said nozzles to form a shroud therearound, the curtainextending substantially to said filter wall, and means for supplying airto the nozzles to exit therefrom at such speed that in use of the filterunit the flow of air from the inlet chamber to the outlet chamber isreversed through a filter element when it is in alignment with a nozzle,said air supply means comprising an electrically driven fan unit mountedoutside said outlet chamber and movable ducting connecting said inletport of the manifold to said fan unit.
 2. A self cleaning air filterunit according to claim 1, wherein said movable ducting comprises afirst duct, a port in a wall of said outlet chamber, said first ductbeing connected to said port by means of a first swivel joint, a secondduct and a second swivel joint arranged between the first and secondducts, and a third swivel joint arranged between the second duct andsaid inlet port of said manifold.